Why are spiders so hairy?

Why are spiders so hairy?

Spider hairs perform many important functions, many of which are sensory. Some hairs are sensitive to touch, others detect chemicals (in a similar way to how we taste and smell), and others allow them to climb smooth surfaces. Spiders also have long fine hairs called trichobothria which are sensitive to fine air movement. This allows them to detect prey or threats to them in total darkness.

An Australian Tarantula (Selenotypus species), a hairy burrowing spider from inland northern Australia. It has numerous long fine sensory hairs on its body and legs, microscopic hairs on its feet for grip and climbing, and the dense hair on its body helps to prevent drowning during flash floods by trapping air around the spider.